/*

  * #%L

  * SingleDocumentReplyCallback.java - mongodb-async-driver - Allanbank Consulting, Inc.

  * %%

  * Copyright (C) 2011 - 2014 Allanbank Consulting, Inc.

  * %%

  * Licensed under the Apache License, Version 2.0 (the "License");

  * you may not use this file except in compliance with the License.

  * You may obtain a copy of the License at

  * 

  *      http://www.apache.org/licenses/LICENSE-2.0

  * 

  * Unless required by applicable law or agreed to in writing, software

  * distributed under the License is distributed on an "AS IS" BASIS,

  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

  * See the License for the specific language governing permissions and

  * limitations under the License.

  * #L%

  */

 package com.allanbank.mongodb.client.callback;

 import java.util.List;

 import com.allanbank.mongodb.Callback;

 import com.allanbank.mongodb.MongoDbException;

 import com.allanbank.mongodb.bson.Document;

 import com.allanbank.mongodb.client.message.Reply;

 import com.allanbank.mongodb.error.ReplyException;

 /**

  * Callback to expect and extract a single document from the reply.

  * 

  * @api.no This class is <b>NOT</b> part of the drivers API. This class may be

  *         mutated in incompatible ways between any two releases of the driver.

  * @copyright 2011-2014, Allanbank Consulting, Inc., All Rights Reserved

  */

 public class SingleDocumentReplyCallback extends

         AbstractReplyCallback<Document> {

     /**

      * Create a new SingleDocumentReplyCallback.

      * 

      * @param results

      *            The callback to notify of the reply document.

      */

     public SingleDocumentReplyCallback(final Callback<Document> results) {

         super(results);

     }

     /**

      * {@inheritDoc}

      * <p>

      * Creates an exception if the {@link Reply} has less than or more than a

      * single reply document.

      * </p>

      * 

      * @param reply

      *            The raw reply.

      * @return The exception created.

      */

     @Override

     protected MongoDbException asError(final Reply reply) {

         MongoDbException error = super.asError(reply);

         if (error == null) {

             final List<Document> results = reply.getResults();

             if (results.size() != 1) {

                 error = new ReplyException(reply,

                         "Should only be a single document in the reply.");

             }

         }

         return error;

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to return the reply document.

      * </p>

      * 

      * @see AbstractReplyCallback#convert(Reply)

      */

     @Override

     protected Document convert(final Reply reply) throws MongoDbException {

         final List<Document> results = reply.getResults();

         if (results.size() == 1) {

             return results.get(0);

         }

         return null;

     }

 }